1. Field of the Invention
The present invention relates to a mechanism for establishing the clearance between a housing and a seaming cam lever for swinging a pair of seaming rolls in a machine for double-seaming, a can end on a can body.
2. Description of Background Art
Can end double-seaming machines generally have, as major components, a lifter, a seaming chuck, and a seaming roll. When a can end is to be seamed on a can body, the cam body which is supported on the lifter and the can end which is placed on the can body with the seaming chuck fitted therein are held between the seaming chuck and the lifter. Then, the seaming roll is moved toward the seaming chuck, seaming the can end on the can body by plastically deforming a cover hook of the can end and a flange of the can body in interengaging relationship to each other. The seaming roll comprises first and second seaming rolls. The first seaming roll effects a first stage of seaming, and then the second seaming roll effects a second stage of seaming, thereby double-seaming the can end on the can body.
FIG. 4 shows a known mechanism (hereinafter referred to as a seaming roll mechanism) including the seaming roll of the double-seaming machine.
The seaming roll mechanism comprises a housing a rotatable around a main shaft (not shown) of the doubleseaming machine, and an angularly movable shaft b extending vertically through a hole a1 defined in a marginal edge portion of the housing a and extending between upper and lower surfaces of the housing a. The shaft b has an upper end b1 projecting above the upper surface of the housing a, and a seaming cam lever c is integrally fitted over the projecting end b1 of the shaft b. The shaft b also has a lower end b2 projecting below the lower surface of the housing a, and a seaming roll lever d is integrally fitted over the projecting end b2. The seaming lever c, the shaft b, and the seaming roll lever d are normally urged upwardly by a spring e inserted in an upper portion of the housing and held against the seaming cam lever c through a plug f.
A pair of roll pins g is vertically inserted in the seaming lever d at positions one on each side of the shaft b. The roll pins g have lower ends projecting below the seaming roll lever d, and first and second seaming rolls h, i are rotatably fitted over the projecting lower ends of the roll pins g. The seaming roll lever d is threaded over the lower end b2 of the shaft b. A lock screw j is threaded through a side of the seaming roll lever d toward the shaft b, and has a tip end pressed against the bottom of a recess k which is defined in a side of the lower end of the shaft b, thereby fixing seaming roll lever d to the shaft b. A pair of washers l is interposed between the upper surface of the seaming roll lever d and the lower surface of the housing a, the washers l being disposed around the shaft b.
The seaming cam lever c has a cam follower pin n that is vertically fixed to a distal end of an arm m which extends horizontally from a portion of the seaming cam lever c which is securely fitted over the upper end of the shaft b. A cam follower o is rotatably mounted on the cam follower pin n by bearings r. The cam follower o is rollingly disposed in a cam groove q which is defined in a cam frame p that is positioned above the housing a. The cam groove q extends around the main shaft of the doubleseaming machine such that when the housing a and the shaft b are angularly moved around the main shaft, the cam groove q guides the cam follower pin n to turn the shaft b around the axis thereof. As the housing a is angularly moved around the main shaft, the seaming cam lever c is turned by the cam follower o riding in the cam groove q to angularly move the shaft b to turn the seaming roll lever d, thus angularly moving the first and second seaming rolls h, i successively toward the seaming chuck s.
The shaft b is disposed in the housing a with bushings u, v interposed therebetween. An expandable and contractable O-ring x is interposed between the lower end of the lower bushing v and the upper washer l.
Normally, there is a clearance Cl between the lower surface of the seaming cam lever c and the upper surface of the housing a. The clearance Cl allows the seaming cam lever c to move smoothly with respect to the housing a even when the seaming cam lever c is thermally expanded while operating at high speed during operation of the double-seaming machine.
As shown in FIG. 5, it is generally necessary to keep the seaming roll h, i and the seaming chuck s vertically spaced by a gap t of several tens .mu.m in order to avoid mutual interference between the seaming rolls h, i and the seaming chuck s when the seaming rolls h, i and the seaming chuck s approach each other, thereby allowing the can end to be seamed appropriately on the can body. When shaft b turns the seaming roll lever d, the shaft b may be depressed under the bias of the spring e. Therefore, the clearance Cl should be set up with the same accuracy as that for the gap t so that the clearance Cl will not adversely affect the gap t.
Heretofore, the clearance Cl has been set to a desired magnitude by manually adjusting the seaming roll lever d with respect to the shaft b when the seaming roll lever d is to be fixedly mounted on the shaft b.
More specifically, the shaft b with the seaming cam lever c attached to the upper end thereof is inserted vertically through the housing a. Then, while the shaft b and the seaming cam lever c are being lowered against the bias of the spring e, the seaming roll lever d is threaded over the lower end of the shaft b. To establish the clearance Cl, the seaming roll lever d is threaded up to a suitable position on the lower end of the shaft b. Thereafter, the seaming roll lever d is brought against the lower surface of the housing a through the washers l under the resiliency of the spring e. In order to set up the gap t as well as the clearance Cl, the threaded position of the seaming roll lever d is adjusted while measuring the gap t and the clearance Cl with a thickness gage, a dial gage, or the like. After such adjustment, the seaming roll lever d is secured to the shaft b by the lock screw j.
Therefore, it has been customary to adjust the gap t between the seaming rolls h, i and the seaming chuck s below the housing a while measuring the gap t with a thickness gage or the like, and also to adjust the fixed position of the seaming roll lever d with respect to the shaft b below the housing a while measuring the clearance Cl with a dial gage or the like. Consequently, it has been cumbersome and time-consuming to establish the clearance Cl, and it has taken a long period of time to install the seaming roll lever d in position.